LONDON - Stable angina is as common in women as in men and is more dangerous than previously thought, researchers here reported.

Action Points

Explain to interested patients that stable angina in a woman may be the first sign of heart disease and is not a benign condition.

Recognize that while myocardial infarction announces heart disease in men, angina in women is not a "soft" diagnosis and deserves follow-up studies.

LONDON, March 21 - Stable angina is as common in women as in men and is more dangerous than previously thought, according to researchers here.

In contrast to myocardial infarction, which has a higher rate in men, angina in women is often the first sign of heart disease and is associated with increased coronary mortality compared with women in the general population, said Harry Hemingway, FRCP, of University College London and colleagues.

Angina in women is not benign in terms of death rates, and among certain subgroups, such as diabetics, the annual heart attack risk was one in 10, similar to that of men, the investigators reported in the March 22/29 issue of the Journal of the American Medical Association. The findings emerged from a prospective cohort collaborative study in Finland funded by the British Heart Foundation.

"To our knowledge," they added, "this study represents the first large-scale investigation of angina as an initial symptomatic manifestation of coronary heart disease," Dr. Hemingway said. "The subject of long-standing debate, angina in women occurs in the general population as commonly as in men, and its prognostic impact suggests that it should not be discounted as a benign or soft diagnosis."

He said that angina has been a "Cinderella in heart disease research because of the difficulties in establishing which patients have angina-many people with symptoms are not tested-and because most patients are not hospitalized." The opposite is not true for heart attacks. Nearly all patients are tested to confirm the diagnosis and are admitted to a hospital, he said.

In an electronic record study of more than 100,000 patients, ages 45 to 89, who had no history of coronary disease, the researchers found that women had a similarly high rate of stable angina compared with men. The age-standardized annual incidence per 100 population of all cases of angina was 2.03 in men and 1.89 in women, with a sex ratio of 1.07 (95% CI 1.06-1.09).

For the study, researchers defined two categories of new cases: "nitrate angina," based on a nitrate prescription (56,441 women and 34,885 men) or "test-positive angina," based on abnormal invasive or noninvasive test results (11,391 women and 15,806 men).

At every age, nitrate angina in women and men was associated with a similar increase in the risk of coronary mortality relative to the general population. Women using higher doses of nitrates had prognoses comparable to that of men, the researchers said.

Women with test-positive angina who were younger than 75 had higher coronary-standardized mortality ratios than men. For example, among those ages 55 to 64, the ratio was 4.69 (95% CI, 3.60-6.11) in women compared with 2.40 (95% CI, 2.11-2.73) in men (P= 0.001 for interaction).

Women tended to have fewer coronary events than men, although the female advantage diminished or was absent among clinical subgroups, particularly women with diabetes. Among patients with diabetes and test-positive angina, age-standardized coronary event rates were 9.9 per 100 person-years in women versus 9.3 in men (P=0.69). The fully adjusted male-female sex ratio in these patients was 1.07 (95% CI, 0.81-1.41), the researchers reported.

As a group, women had a lower rate than men of test-positive cases of angina, and a reported "underuse" of testing if they had chest pain. This underuse of angiograms and treadmill tests may be related to differences in symptom description or physician perception, the researchers said. Drug treatment, the researchers said, was frequently prescribed on the basis of symptoms alone without diagnostic tests.

Absolute rates of coronary events in women were high when compared with thresholds for starting secondary prevention treatment, the researchers found. "Novel functional imaging studies suggest that among women with angina and non-obstructed coronary arteries (more common in women than in men with chest pain), imaging techniques may reveal hitherto undetected evidence of ischemia associated with increased coronary event rates," the researchers said.

"To our knowledge," they added, "this study represents the first large-scale investigation of angina as an initial symptomatic manifestation of coronary heart disease, Dr. Hemingway said. "The subject of long-standing debate, angina in women occurs in the general population as commonly as in men, and its prognostic impact suggests that it should not be discounted as a benign or soft diagnosis."

"We need to understand why women are relatively protected from heart attack but not from angina, and ensure fair access to investigation and treatment services," the researchers said.